C#字符串中的中文逗号转英文逗号

public static string ToDBC(string input)
{
char[] c = input.ToCharArray();
for (int i = 0; i < c.Length; i++)
{
if (c[i] == 12288)
{
c[i] = (char)32;
continue;
}
if (c[i] > 65280 && c[i] < 65375)
c[i] = (char)(c[i] - 65248);
}
return new string(c);
}